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At least 235 records · Page 13

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NASA NTRS1985

A First Look at Airborne Imaging Spectrometer (AIS) Data in an Area of Altered Volcanic Rocks and Carbonate Formations, Hot Creek Range, South Central Nevada

Three flight lines of Airborne Imaging Spectrometer (AIS) data were collected in 128 bands between 1.2 and 2.4 microns in the Hot Creek Range, Nevada on July 25, 1984. The flight lines are underlain by hydrothermally altered and unaltered Paleozoic carbonates and Tertiary rhyolitic to latitic volcanics in the Tybo mining district. The original project objectives were to discriminate carbonate rocks from other rock types, to distinguish limestone from dolomite, and to discriminate carbonate units from each other using AIS imagery. Because of high cloud cover over the prime carbonate flight line and because of the acquisition of another flight line in altered and unaltered volcanics, the study has been extended to the discrimination of alteration products. In an area of altered and unaltered rhyolites and latites in Red Rock Canyon, altered and unaltered rock could be discriminated from each other using spectral features in the 1.16 to 2.34 micron range. The altered spectral signatures resembled montmorillonite and kaolinite. Field samples were gathered and the presence of montmorillonite was confirmed by X-ray analysis.

Feldman, S. C.↗

NASA NTRS1986

Spectral mixture modeling - A new analysis of rock and soil types at the Viking Lander 1 site

A Viking Lander 1 image was modeled as mixtures of reflectance spectra of palagonite dust, gray andesitelike rock, and a coarse rocklike soil. The rocks are covered to varying degrees by dust but otherwise appear unweathered. Rocklike soil occurs as lag deposits in deflation zones around stones and on top of a drift and as a layer in a trench dug by the lander. This soil probably is derived from the rocks by wind abrasion and/or spallation. Dust is the major component of the soil and covers most of the surface. The dust is unrelated spectrally to the rock but is equivalent to the global-scale dust observed telescopically. A new method was developed to model a multispectral image as mixtures of end-member spectra and to compare image spectra directly with laboratory reference spectra. The method for the first time uses shade and secondary illumination effects as spectral end-members; thus the effects of topography and illumination on all scales can be isolated or removed. The image was calibrated absolutely from the laboratory spectra, in close agreement with direct calibrations. The method has broad applications to interpreting multispectral images, including satellite images.

Adams, J. B.↗

NASA NTRS1986

Lithologic mapping of silicate rocks using TIMS

Common rock-forming minerals have thermal infrared spectral features that are measured in the laboratory to infer composition. An airborne Daedalus scanner (TIMS) that collects six channels of thermal infrared radiance data (8 to 12 microns), may be used to measure these same features for rock identification. Previously, false-color composite pictures made from channels 1, 3, and 5 and emittance spectra for small areas on these images were used to make lithologic maps. Central wavelength, standard deviation, and amplitude of normal curves regressed on the emittance spectra are related to compositional information for crystalline igneous silicate rocks. As expected, the central wavelength varies systematically with silica content and with modal quartz content. Standard deviation is less sensitive to compositional changes, but large values may result from mixed admixture of vegetation. Compression of the six TIMS channels to three image channels made from the regressed parameters may be effective in improving geologic mapping from TIMS data, and these synthetic images may form a basis for the remote assessment of rock composition.

Gillespie, A. R.↗

NASA NTRS1986

Rock flows

Rock flows are defined as forms of spontaneous mass movements, commonly found in mountainous countries, which have been studied very little. The article considers formations known as rock rivers, rock flows, boulder flows, boulder stria, gravel flows, rock seas, and rubble seas. It describes their genesis as seen from their morphological characteristics and presents a classification of these forms. This classification is based on the difference in the genesis of the rubbly matter and characterizes these forms of mass movement according to their source, drainage, and deposit areas.

Matveyev, S. N.↗

NASA NTRS1985

Enhanced rock discrimination using Landsat-5 Thematic Mapper (TM) data

The application of TM data to rock discrimination is discussed. Sixteen specific terrains derived from geologic maps are examined on TM images of the Arabian shield obtained on Apr. 14, 1984; visual enhancement procedures are applied to the images. The rock types observed in the test site are described; the major sedimentary formations in the test area are laterite and sandstone. The data reveal that the layered rocks in the outcrop consist of a variety of metamorphosed volcanics, metamorphosed sediments, and amphibolite, and the intrusive complex is composed of several classes of mafic and acidic rocks.

Blodget, H. W.↗

NASA NTRS1987

Petrology of gabbroic rocks from the Mid-Cayman rise spreading center

Mineral analyses of oxide and silicate phases from a suite (collected with the DSRV Alvin in January 1976 and July 1977) of 48 gabbroic rocks collected from the vicinity of the Mid-Cayman Rise spreading center are reported. Mineral compositions of these anorthosites, leuco-troctolite, leuco-olivine gabbros, olivine gabbros, leuco-gabbros, and gabbros indicate the cumulate rocks have been produced by the crystal fractionation of basaltic liquids. Certain features of these rocks are inconsistent with the occurrence of this fractionation at low pressures (1 atm to 2 kbar). Although the experimental data are not available to conclusively demonstrate that the effects seen were produced at moderate pressures (5-10 kbar), the effects are similar to those predicted thermodynamically and to those observed in limited experimental studies within this pressure range. It is therefore suggested that the most likely scenario for the production of these gabbroic rocks is the moderate-pressure crystallization of basaltic magmas within deep-seated magma chambers underneath this slow-spreading center.

Elthon, Don↗

NASA NTRS1987

Petrology of the igneous rocks

Papers published during the 1983-1986 period on the petrology and geochemistry of igneous rocks are discussed, with emphasis on tectonic environment. Consideration is given to oceanic rocks, subdivided into divergent margin suites (mid-ocean ridge basalts, ridge-related seamounts, and back-arc basin basalts) and intraplate suites (oceanic island basalts and nonridge seamounts), and to igneous rocks formed at convergent margins (island arc and continental arc suites), subdivided into volcanic associations and plutonic associations. Other rock groups discussed include continental flood basalts, layered mafic intrusions, continental alkalic associations, komatiites, ophiolites, ash-flow tuffs, anorthosites, and mantle xenoliths.

Mccallum, I. S.↗

NASA NTRS1988

Microwave dielectric spectrum of rocks

A combination of several measurement techniques was used to investigate the dielectric properties of 80 rock samples in the microwave region. The real part of the dielectric constant, epsilon', was measured in 0.1 GHz steps from 0.5 to 18 GHz, and the imaginary part, epsilon'', was measured at five frequencies extending between 1.6 and 16 GHz. In addition to the dielectric measurements, the bulk density was measured for all the samples and the bulk chemical composition was determined for 56 of the samples. The study shows that epsilon' is frequency-dependent over the 0.5 to 18 GHz range for all rock samples, and that the bulk density rho accounts for about 50 percent of the observed variance of epsilon'. For individual rock types (by genesis), about 90 percent of the observed variance may be explained by the combination of density and the fractional contents of SiO2, Fe2O3, MgO, and TiO2. For the loss factor epsilon'', it was not possible to establish statistically significant relationships between it and the measured properties of the rock samples (density and chemical composition).

Ulaby, F. T.↗

NASA NTRS1988

Fine-scale traverses in cumulate rocks, Stillwater Complex: A lunar analogue study

The objective was to document finite-scale compositional variations in cumulate rocks from the Stillwater Complex in Montana and to interpret these data in the context of planetary magma fractionation processes such as those operative during the formation of the Earth's Moon. This research problem involved collecting samples in the Stillwater Complex and analyzing them by electron microprobe, X-ray fluorescence (XRF), and instrumental neutron activation analysis (INAA). The electron microprobe is used to determine the compositions of cumulus and intercumulus phases in the rocks, the XRF is used to determine the bulk-rock major element and trace element (Y, Sr, Rb, Zr, Ni, and Cr) abundances, and the INAA lab. is used to determine the trace element (Sc, Co, Cr, Ni, Ta, Hf, U, Th, and the REE) abundances of mineral separates and bulk rocks.

Elthon, Donald↗

NASA NTRS1988

Earth rocks on Mars: Must planetary quarantine be rethought

Recent geochemical, isotopic, and rare gas studies suggest that eight SNC meteorites originated on the planet Mars. Since Martian rocks are found on Earth, consideration is being given to finding Earth rocks on Mars. Detailed consideration of the mechanism by which these meteorites were lofted into space strongly suggest that the process of stress-wave spallation near a large impact with, perhaps, an assist from vapor plume expansion, is the fundamental process by which lightly-shocked rock debris is ejected into interplanetary space. The theory of spall ejection was used to examine the mass and velocity of material ejected from the near vicinity of an impact. It seems likely that the half-dozen largest impact events on Earth would have ejected considerable masses of near surface rocks into interplanetary space. No computations were performed to indicate how long Earth ejecta would take to reach Mars.

Melosh, H. J.↗

NASA NTRS1988

Kaersutite-bearing xenoliths and megacrysts in volcanic rocks from the Funk Seamount in the souhtwest Indian Ocean

The petrography, mineral chemistry, and whole-rock compositions of volcanic rocks dredged from the Funk Seamount, located 60 km NW of Marion Island in the southwestern Indian Ocean, are presented together with the mineral chemistry of their inclusions. On the basis of these characteristics, the possible relationships between the Funk Seamount's volcanic rocks and the megacrysts and xenoliths in these rocks are discussed. It is argued that the Funk Seamount lavas derive from a similar mantle source region as that of the Marion Island and Prince Edward Island hotspot lavas. The geochemical signature of these lavas implies derivation from a source that is enriched (e.g., in Ti, K, P, and Nb) over the depleted mantle source regions for the adjacent mid-ocean ridge basalts.

Reid, Arch M.↗

NASA NTRS1990

Geochemistry of Darwin impact glass and target rocks

Results are presented from major and trace element composition analyses of 18 Darwin (Australia) glass samples and seven target rocks from the Darwin crater area. It is found that the chemical composition of the glass samples is in agreement with an origin from terrestrial sediments during an impact. Analyses of the target rocks from the Darwin crater and mixing calculations show that the Darwin glass can be formed from the local target rocks. Evidence is presented for a loss of the volatile elements Ga, Zn, F, and B during the impact event. The elements Na, K, Rb, and Cs show lower abundance in the glass than in the target rocks. This suggests selective volatilization from the impact melt.

Meisel, Thomas↗

NASA NTRS1990

Microwave dielectric properties of dry rocks

A combination of techniques was used to measure the dielectric properties of 80 rock samples in the microwave region. The real part (RP) of the relative dielectric constant was measured in 0.1-GHz steps from 0.5 to 18 GHz, and the imaginary part (IP) was measured at five frequencies between 1.6 and 16 GHz. The bulk density rho(b) was also measured for all the samples, and the bulk chemical composition (BCC) was determined for 56 of the samples. RP is found to be frequency-independent at 0.5-18 GHz for all samples, and rho(b) accounts for about 50 percent of the observed variance. For silicate rocks, as much as 78 percent of the variance is explained by the combination of rho(b) and the fractional contents of oxides when the silicates are subgrouped by genesis. In contrast, IP decreases with increasing frequency for most rock samples, and no statistically significant relationships are found between IP and rho(b). For subgrouped silicate rocks, 60 percent of the variance in IP can be explained by BCC.

Ulaby, Fawwaz T.↗

NASA NTRS1990

Effect of leading edge roundness on a delta wing in wing-rock motion

The effect of wing leading-edge roundness on wing rock was investigated using flow visualization in a water tunnel. Eighty degree delta wing models were tested on free-to-roll and forced oscillation rigs. The onset of wing rock was delayed by increasing the roundness of the leading edges. The wing rock amplitude and frequency results suggested that damping was increased at lower angles of attack but reduced at higher angles of attack. Vortex lift-off and vortex breakdown, especially during dynamic situations, were strongly affected by the leading edge roundness. Different forms of wing rock motion could be sustained by combinations of vortex breakdown and vortex lift-off. Behaviors of the wing and vortex motions were explained by the influence of leading edge roundness on the separation location, vortex trajectory, and vortex breakdown.

Ng, T. Terry↗

NASA NTRS1990

Getting lunar ilmenite - From soils or rocks?

Lunar soils or rocks can be mined as sources of ilmenite for producing oxygen. However, separable crystals of loose ilmenite in lunar soils are rare (less than 2 percent) and small (less than 200 microns); most ilmenite in the regolith is locked together with silicate minerals as rock fragments. If fragmentation of rock sources must be attempted to win appreciable amounts of ilmenite (approximately 10 percent or more), selective collection of high-Ti basalt fragments larger than 1 cm for fragmentation and ilmenite beneficiation may be advantageous over extensive processing of fine lunar soil. Many alternative processing schemes for fragmenting rocks on the Moon have been proposed; one process which was tested early in the Apollo program successfully disaggregated lunar and terrestrial basalts by passive exposure to low-pressure alkali (K) vapor. This process is worthy of reinvestigation.

Vaniman, D. T.↗

NASA NTRS1991

Wing rock suppression using forebody vortex control

Static and free-to-roll tests were conducted in a water tunnel with a configuration that consisted of a highly-slender forebody and 78-deg sweep delta wings. Flow visualization was performed and the roll angle histories were obtained. The fluid mechanisms governing the wing rock of this configuration were identified. Different means of suppressing wing rock by controlling the forebody vortices using small blowing jets were also explored. Steady blowing was found to be capable of suppressing wing rock, but significant vortex asymmetries had to be induced at the same time. On the other hand, alternating pulsed blowing on the left and right sides of the forebody was demonstrated to be potentially an effective means of suppressing wing rock and eliminating large asymmetric moments at high angles of attack.

Ng, T. T.↗

NASA NTRS1993

An aerodynamic model for one and two degree of freedom wing rock of slender delta wings

The unsteady aerodynamic effects due to the separated flow around slender delta wings in motion were analyzed. By combining the unsteady flow field solution with the rigid body Euler equations of motion, self-induced wing rock motion is simulated. The aerodynamic model successfully captures the qualitative characteristics of wing rock observed in experiments. For the one degree of freedom in roll case, the model is used to look into the mechanisms of wing rock and to investigate the effects of various parameters, like angle of attack, yaw angle, displacement of the separation point, and wing inertia. To investigate the roll and yaw coupling for the delta wing, an additional degree of freedom is added. However, no limit cycle was observed in the two degree of freedom case. Nonetheless, the model can be used to apply various control laws to actively control wing rock using, for example, the displacement of the leading edge vortex separation point by inboard span wise blowing.

Hong, John↗

NASA NTRS1992

Prediction and control of slender-wing rock

The unsteady Euler equations and the Euler equations of rigid-body dynamics, both written in the moving frame of reference, are sequentially solved to simulate the limit-cycle rock motion of slender delta wings. The governing equations of the fluid flow and the dynamics of the present multidisciplinary problem are solved using an implicit, approximately-factored, central-difference-like, finite-volume scheme and a four-stage Runge-Kutta scheme, respectively. For the control of wing-rock motion, leading-edge flaps are forced to oscillate anti-symmetrically at prescribed frequency and amplitude, which are tuned in order to suppress the rock motion. Since the computational grid deforms due to the leading-edge flaps motion, the grid is dynamically deformed using the Navier-displacement equations. Computational applications cover locally-conical and three-dimensional solutions for the wing-rock simulation and its control.

Kandil, Osama A.↗